1. Field of the Invention
The subject invention generally pertains to riding lawnmowers, and more specifically, to a means for dynamically leveling the seat.
2. Description of Related Art
In operating a riding lawnmower tractor, it is desirable to shift one's weight to compensate for the tractor tilting while traversing hills and to compensate for centrifugal force when turning. For rider comfort, it is also nice to keep the seat level.
There is an important distinction between shifting the operator's weight and just simply keeping the seat level. Leveling the seat is primarily for comfort, while properly shifting the operator's weight can improve traction and safety. While traversing hills, the uphill wheel can lose traction, as weight shifts to the lower wheel. On a hill, it is desirable to have the operator's center of gravity directly above a point on the ground that is halfway between the two wheels. Shifting the operator's weight even closer to the uphill wheel is even better, as it helps compensate for the tractor's center of gravity shifting downhill.
U.S. Pat. Nos. 3,466,089; 4,515,377; and 5,372,347 each have seat leveling devices. But in each case, the operator's weight is not shifted to where it belongs. In the FIG. 1 of each device, it is clear that when projecting a line straight downward from the operator's center of gravity, that line intersects the surface of the ground at a point closer to the downhill wheel. The farther downhill the weight is shifted, the greater is the traction imbalance and likelihood of tipping.
The very same problem exists with the devices of U.S. Pat. Nos. 4,636,001 and 5,054,739. However, the problem is not as apparent, because the drawing figures do not illustrate how an operator's weight is shifted relative to a tractor. Nonetheless, the same problem exists unless the seat is virtually set at ground level.
The self-leveling seat of U.S. Pat. No. 3,632,076 appears worst of all. The seat frame actually shifts closer to the downhill wheel.